Press release: Clues from the skin tissues of a Jurassic ichthyosaur
No. 263 - 05.12.2018
An international team of researchers with participation from the University of Göttingen has investigated the skin and pigmentation of a fossil ichthyosaur. The results were published in the journal Nature.
Ichthyosaurs are extinct marine reptiles that resemble modern toothed whales, such as dolphins. Their similar appearance suggests that ichthyosaurs and whales evolved similar strategies to adapt to marine life. For instance, ichthyosaurs have long been suspected to be warm-blooded, but the limited preservation of their fossils has made this and other similarities difficult to confirm.
The animal studied belonged to the genus Stenopterygius which lived in the early Jurassic period about 180 million years ago. Its habitat was a shallow sea which, at that time, covered large parts of southern Germany. The researchers found remnants of the animal’s original, smooth skin that was still flexible and comprised of distinct inner (dermal) and outer (epidermal) layers, with fat layers (blubber) underneath. "Blubber is characteristic of present-day marine mammals," says Professor Volker Thiel from the Geoscience Centre of the University of Göttingen and co-author of the study, "it insulates the animals against the cold, aids buoyancy and acts as an energy store. The finding of blubber remnants confirms that ichthyosaurs were warm-blooded.”
In addition, the authors find that the ichthyosaur skin is pigmented in a pattern that suggests the reptiles were ‘countershaded’ — having a light underbelly and a darker upper surface. "In the fossil skin we identified highly branched pigment cells that still contained melanin” said Professor Thiel. "This pigment occurs in many modern animals and is, for example, responsible for the dark colouring of human hair”. A colour distribution with a light underside and a dark top also occurs in whales and many other marine animals. It can act as camouflage, protect against UV light when staying at the water surface and support heat regulation.
“Our study reveals that the similarities between ichthyosaurs and today's toothed whales are not only skin deep, but extend to the ultrastructural and molecular level. This highlights the evolutionary convergence of two very different groups of animals and their shared adaptation to marine life," says Thiel.
Original publication: Johan Lindgrenet al. Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur. Nature (2018). https://doi.org/10.1038/s41586-018-0775-x
Professor Volker Thiel
University of Göttingen
Department of Geobiology
+49 (0) 551 3914395